Amyotrophic lateral sclerosis (ALS) is one of the most devastating neurological diseases. It affects upper and lower motor neurons (UMN and LMN). The cause is largely unknown, so no effective treatments are available. To date, "no objective and quantitative UMN or LMN markers" are available---one of most serious deficiencies in ALS. Thus, "understanding of the pathogenesis of UMN and LMN involvement" is limited, and no reliable early diagnosis and effective surrogate markers are available. Therefore, we propose (1) to investigate several novel technologies to establish accurate UMN and LMN markers, (2) to investigate whether these markers provide early diagnosis and clinically meaningful natural history data that indicate changes over time with high sensitivity, (3) to identify whether these markers prognosticate ALS disability and survival, and (4) to validate histologically the changes observed with technology- identified markers. First, test-retest validity and normal data will be established in healthy controls using emerging neuroimaging technologies at two hospital campuses. In patients with suspected/possible ALS or probable/definite ALS, we will investigate quantitative evidence for (1) UMN involvement at the motor cortex area by single-voxel magnetic resonance spectroscopy (MRS) and more accurately at the primary motor cortex by multiple-voxel MRS; (2) fiber tract integrity of descending UMN fiber tracts by MR diffusion tensor imaging; and (3) physiological integrity of the corticospinal tracts using transcranial magnetic stimulation technology. An LMN marker will be studied by motor unit number estimation using multiple point stimulation technology. ALS status will be measured by well- validated quantitative clinical assessments. The patients will be followed every 3 months for 15 months. The potential value of the technology-identified markers for use as surrogate markers as endpoints in clinical trials will be analyzed by statistical modeling. Functional disability and survival also will be correlated with these markers. When autopsy is permitted, technology-identified markers will be validated histologically. To our knowledge, this project will be the first comprehensive approach to investigate ways to develop a reliable and early diagnosis of ALS, to develop surrogate markers in clinical trials, and to improve prognostication in ALS. The knowledge gained from this project not only will expand understanding of the pathogenesis of UMN and LMN involvement in ALS, but also will permit more effective clinical trials of new drugs in the near future and improve diagnosis and treatment for patients with this disease.